As a chemical/physical phenomenon detecting device, a cumulative chemical/physical phenomenon detecting device disclosed in Patent Document 1 is known.
This detection device is used as, for example, a pH sensor, and removes the influence of remaining charges due to a potential barrier (so-called “bump” of potential). The remaining charges can be a factor in generating a false signal so that the charges should be removed to perform high-sensitivity detection.
In a prior chemical/physical phenomenon detection device, this potential barrier is formed at a position adjacent to the first charge control electrode which defines the potential of an Input Charge Control (ICG) region. That is, a silicon nitride film defining the sensing region on the substrate inherently covers the first charge control electrode according to the manufacturing process of the device, so that the silicon nitride film becomes thick on the side surface of the first charge control electrode. Hence, the external environment is not sufficiently reflected in the potential change of the substrate.
As a method for removing the influence of the remaining charges due to the potential barrier, a charge removal well is provided between the input charge control region and the sensing region. By controlling the potential of this removal well, the remaining charges in the sensing region are forcedly attracted to this removal well, thereby preventing the generation of the false signal.